Embodiments herein generally relate to a printing apparatus (e.g., electrostatographic and/or xerographic machine and/or process) and more particularly relate to an energy storage device that is useful within drive nips, such as the drive nips of a printing apparatus.
In drive nips, opposing rollers are biased against one another. The details of drives nips are only briefly touched upon in this disclosure; however, an extensive discussion of such structures can be found in U.S. Pat. Nos. 6,173,952; and 6,168,153, the complete disclosures of which are incorporated herein by reference. Briefly, the drive nips comprise drive rollers and corresponding idler rollers opposite the drive rollers. The drive roller is driven by a motor and the idler roller is biased against the drive roller and freely rotates with the drive roller to cause a piece of media (paper, transparencies, cardstock, etc.) to be moved through the drive nip. A drive axle is operatively connected to the drive rollers. The drive axle rotates in a forward direction when moving media through the media drive nip.
In addition, one or more cams are operatively connected to corresponding idler rollers by way of cam followers. The cam followers transfer movement of the cams to the idler rollers. As the cams rotate, the cams move the idler rollers between a first position biased against the drive rollers and a second position out of contact with the drive rollers. The cams can be shaped and positioned to move pairs of the idler rollers differently as the cams rotate to accommodate different media widths. Thus, for example, one set of cams could cause only the outer pair of idler rollers to be biased against their corresponding drive rollers for wide media, while another set of cams could cause just an inner pair of idler rollers to be biased against their corresponding drive rollers to accommodate a narrower piece of media. In addition, drive nips can be individually engaged to align the media.
Thus, the nip release assembly includes spring loaded idler rolls that are raised, or lowered, using a cam/follower mechanism driven by a stepper motor. In some situations, two of the idler rolls can be raised and lowered in pairs, while a third idler can remain in the raised position. The peak torque, reflected to the stepper motor, can occur as a pair of idler rolls is raised.
There is a delicate balance between speed/acceleration of actuation and the reflected torque on the stepper motor. While increased actuation speeds/accelerations require increased motor torque to overcome the inertial effects, scaling the motor up to handle larger torque loads is not always viable. Upgrading to a larger motor may be prohibitive because of cost, size, larger rotor inertia, etc. A common approach is to design and model a system where the motor is sized properly to operate with the reflected torque.
Embodiments herein address such issues with an energy storage device connected to the camshaft. Many devices could use such an apparatus, such as a printing apparatus that could have at least one media drive nip. More specifically, embodiments herein provide an energy storage apparatus used in a drive nip, a printing device that includes such an apparatus, a module installable in a printing device that uses such an apparatus, etc.
The energy storage apparatus has one or more camshafts, one or more cams connected to the camshaft, one or more followers contacting the cam, one or more biasing members connected to the follower, and one or more tracks or spring loaded followers on a pivot arm (idler arm using a torsion spring) connected to the follower. With embodiments herein the track can limit movement of the follower to a curved or linear constrained path intersecting the axis about which the camshaft rotates. Alternatively, the biasing member itself can limit the movement of the follower to this linear path. The biasing member can comprise any force member such as a spring, a piston, a flexible member, a compressible member, etc. that has the ability to bias the roller toward the axis of the camshaft.
The apparatus can also include a stationary frame connected to the biasing member. More specifically, the biasing member has a first end connected to the follower and a second end connected to the frame (which could be the main frame). The biasing member stores potential energy as the follower moves away from the axis of the camshaft, and the biasing member releases stored potential energy as the follower moves toward the axis of the camshaft. As the biasing member releases the stored potential energy, it eases the load of the motor driving the camshaft, thereby decreasing peak torque requirements of the motor. The potential energy is transferred to the follower on the idler member. As one stores potential energy, the other releases potential energy, canceling each other.
These and other features are described in, or are apparent from, the following detailed description.